ObservableCollection does not get updated. Why?

Question

In my MVVM I have a list of ObservableCollection<T> type 
This list gets displayed in a grid.
I also have a button to delete an item from the list.
When I delete an item, I delete it from the database, not from a list.
However the list does not get updated if I don't call for a method that reloads the data into the list after this operation.
So it's pretty much the same as List<T>
Because in both cases I still have to call for a method that reloads the data in the list.
But I understand that ObservableCollection should resolve it on it's own...
Am I missing something?